diff --git a/src/test/run-pass/issues/issue-18804/main.rs b/src/test/run-pass/issues/issue-18804/main.rs
index 2abcd4b7ba99c..f08c5bc71efca 100644
--- a/src/test/run-pass/issues/issue-18804/main.rs
+++ b/src/test/run-pass/issues/issue-18804/main.rs
@@ -17,6 +17,9 @@
 
 // aux-build:lib.rs
 
+// rust-lang/rust#54143: This test *requires* optimizations to be turned on.
+// compile-flags: -O
+
 extern crate lib;
 
 fn main() {